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snoop.daub writes "Dr. Tom Murphy, professor of astrophysics at UCSD, has a new blog called 'Do The Math,' and the first few posts are doozies. In the first, he shows the impossibility of continued exponential growth in energy use. Even if a new, 'free' energy source is developed, thermodynamic limits on efficiency mean that the heat associated with converting this energy into useful work will increase the temperature of the earth to unbearable levels within 300 years. In the second, he extends the argument to economic growth. The timescales there are faster, only 50-100 years. Fascinating stuff. Time to stop breeding, folks, or to get our butts into space."

The big problem with his assumption is that in 1400 years our knowledge of physics doesn't change. It's like an an aysos in the 1800s saying we won't be able to keep our homes lit because we will have killed off all the whales. I'm not saying I know the answer, just I am smart enough not to claim exponential energy growth using today's technology.

Exponential growth in any real (not imaginary/virtual) system must slow down when it exceeds some percentage of it's total environment. Eventually, it hits a saturation point and must slow down. While the exact percentage that defines saturation varies with the growth rate and environment, typically exponential growth can't continue once it reaches 50% of it's environment. So, on a very basic level, he has simply stated the obvious.

However, as heat can be converted to other forms of energy, there are ways to dissipate and/or use the surplus heat. Also, higher efficiency methods of converting heat into electricity or other useful forms of energy will delay the saturation point. So, he's correct in theory, and his details are probably not an accurate prediction.

No, you're simply claiming perpetual technological growth to compensate for physical limits. At some point you hit diminishing returns - even with technology. Compare a Pentium III from 10 years ago to a Quad Core i7 from today. Yeah today's machines are faster and have more memory - but not stunningly so. In fact, there's not so much difference between the machines as a 1977 XT with 128k, a tape drive and a monochrome monitor and a 1987 80386 with megabytes of memory, megabytes of hard disk space, a VGA monitor, sound card, multitasking, etc. Now leap forwards to 1997 and your Pentium II... better but only incrementally so.

You could argue that this scenario is specific to computers but it's not. This is why you don't have your flying car. This is why life expectancy has shot up from 50-odd years to the seventies and is hovering there. This is why cancer patients live longer free of the symptoms of their disease, but the overall mortality of their disease hasn't changed much. There are hard limits to technology, too. It would be foolish to ignore them.

The difference is that his statement is based on natural laws, rather than assumptions about the source of the energy. Unless the fundamental laws of thermodynamics turn out to be wildly incorrect, his statement will stand.

Denying this by claiming that technology will always improve is like denying that there's an end to Moore's law. Yes, we've been able to find ways to keep it going so far. But by 2150, some quick math says that transistors would need to be smaller than the Planck length. It requires some serious magical thinking to believe that not only will we reach that target, but that we'll be able to keep making them even smaller than that!

Think very hard about what is unique and unrepeatable about this moment in history. Now extrapolate 50 years ahead. All of a sudden, those remarkable, delicate and doomed circumstances that make your life so pleasant right now - DON'T EXIST (food, clean air, water, infrastructure, toys, relative afflluence, relative safety). Just because they have existed during the few years you've been alive doesn't mean that happy circumstance shall continue. All available evidence, and any thorough projection (yes, there have been many over the past half a century, mostly with essentially the same clear message), makes it pretty clear this brief light bright period in the West is ending. It didn't have to be this way but a lot of very poor choices were made (and continue to be made).

So you approve of an unfair society where people are given things that they did not earn by having it forcefully taken from someone who did earn it? Call me crazy, but doesn't the dictionary define that sort of behavior as "theft"?

Also, I find it horribly ironic that you talk about the evil "greedy" people, yet you fail to see the greed in thinking you should get something that you didn't earn.

In fact, there's not so much difference between the machines as a 1977 XT with 128k, a tape drive and a monochrome monitor and a 1987 80386 with megabytes of memory, megabytes of hard disk space, a VGA monitor, sound card, multitasking, etc. Now leap forwards to 1997 and your Pentium II... better but only incrementally so.

Yikes! Did you REALLY just use that as an example? Right now I have sitting in front of me my phone. It can curb stomp a Pentium II in raw computing power. It uses a couple of orders of magnitude less power, has a couple of orders of magnitude more storage capacity, it has the capacity to send and/or receive on a half a dozen different signals, has a handful of sensors on it that you would need a wheel barrel to hold 15 years ago, it costs 1/4 as much, and and it fits in my fucking pocket . Seriously... in-my-fucking-pocket . That isn't "incremental" change. That is orders of magnitude exponential change. That is horse to steam engine in 15 years.

You are living in an age of accelerated technological growth. The only thing your example does is show how amazingly flexible humans are in dealing with it. The fact that your head doesn't blow in two when you realize that you can now communicate with anyone in the world, receive the answer to any question with a well known answer, locate any publicly known place and your relation to it, and do it with a hunk of technology that fits in your pocket and costs chump change, just shows that humans can accept that blue is now red and carry on.

If you were to revert the world to the technology of 20 years ago (which is before the widespread use of E-mail and the world wide web), most industries would implode, most people wouldn't even know how to work, and the global economy would grind to a halt. As an engineer working on those chips you find so dully unremarkable and incremental, I physically wouldn't be able to do my job. I wouldn't even know how to do my job. How the fuck do you run a semi-conductor fab when your most powerful computer is a x386? I know we did it in the past, but fuck if I know how you would even begin to contemplate going back to it. Engineering without storing massive amounts of data, computer assistance, and electronic tracking is like going from shopping in a super market to hunting and gathering. They are barely related.

Just because you take a technological revolution that has remade the earth in stride and 'meh' at instant world wide communication of everything over the course of a decade or two doesn't mean it isn't remarkable. Fuck flying cars. Flying cars are shit next to the internet. You are like someone complaining that the mine must be worthless because you only found a little copper, utterly ignoring that it is encrusted in fucking diamonds.

Finally, if you are really hung up on flying cars, consider the fact that if people were allowed to build flying cars with the same "safety" standards as a 1950's car, you could fill the sky with the little death traps. We just choose to focus on safety and price, instead of speed. I say this as someone who managed to get into a spin at 70 mph, bounce across some guard rails, and walk way from the crash without a single bruise, cut or scrap. Try that in a 1950s death trap.

Technology is changing so rapidly these days that anyone who attempts to make dire predictions of 'physical limits' in the next 50 years should be laughed into oblivion, the same way the fools of the steam age proclaiming the same should have been. The semi-conductor industry (that would be 'computer chips' to the layman) has been crushing proclaimed unmovable "physical limits" that are always 10 years away with clockwork regularity for decades, and that is the industry riding edge of our physical understanding of the world. Most industries have not even scratched the surface of what is possible. Anyone who predicts the end of technological development in our lifetime is a god damn fool like all the fools who made the same prediction before them.